Removal of chromium (VI) from water by porous carbon derived from corn straw: Influencing factors, regeneration and mechanism

Porous carbon is one of the most widely used materials to remove Cr(VI) from polluted water. Here we reported one efficient porous carbon material prepared from corn straw. The results of Fourier transform infrared spectroscopy (FTIR), Energy dispersion spectrum (EDS), and X-ray photoelectron spectroscopy (XPS) indicated that the porous carbon surface had functional groups such as COOH, OH and COC, etc, which could be acted as active sites during the adsorption process. Brunauer-Emmett-Teller (BET) results showed that the surface area and total pore volume of the adsorbent were 2131.181 m2/g and 1.128 cm3/g, respectively. The percentages of micropore surface area and micropore volume achieved 91.93% and 80.43%, respectively. The maximum adsorption capacity of Cr(VI) was 175.44 mg/g at 25 °C with the well-developed microporous structure and abundant oxygen-containing functional groups of porous carbon. The adsorption process was well described by the pseudo-second order model and Langmuir adsorption isotherm model. It was mainly based on chemical adsorption of a single molecular layer, accompanied by ion exchange reaction, Cr(VI) reduction, and complexation, etc. The adsorbent exhibited excellent removal performance of Cr(VI) in the co-existing ions wastewater and electroplating wastewater, and could remain high removal performance for four adsorption-desorption cycles.